Many species are shifting their ranges to higher latitudes and elevations in order to track climate changes. The huge number of citizen science records for the UK, combined with the fact that many species reach either a trailing or leading-edge range margin in the UK, provides the ideal opportunity to quantify changes in species’ distributions and population trends, and study the factors responsible. There are particularly detailed data for butterflies and moths, and we analyse long-term distribution and abundance data sets to examine rates of range shifts, test whether species differ in their responses, and examine why differences arise.
Species have shifted northwards in the UK by about 2km per year over the past four decades, but there is considerable variation in the responses of species to recent climate change. We find that population trends are important predictors of range expansion for butterflies, and that lags in species’ responses to climate change highlight the role of habitat fragmentation in slowing up range shifts. Climate is also an important driver of local extinctions at species’ trailing-edge range margins. We conclude that habitat connectivity is important for conserving species in human-dominated landscapes, and that locations providing climate refuges need to be conserved to help slow-up local extinctions. Our future work is examining the ecological and evolutionary limits to species responses.